Function Sites Identification Of High-Affinity K~+Transporter AtHAK5of Arabidopsis Thaliana

AtHAK5is an important member of the KUP/HAK/KT transporter family, it is a high-affinity K+transporter-encoding gene of Arabidopsis thaliana, its expression is up-regulated in response to potassium deprivation. AtHAK5can be integrated into the plasma membrane under low potassium condition, reflecting an adaptation to low potassium condition. This study aims to find the function sites of high-affinity K+transporter AtHAK5of Arabidopsis thaliana. Ten potential phosphorylation sites were found in AtHAK5amino acid sequence based on bioinformation analysis. We supposed these sites were important for the function of AtHAK5,17amino acids were selected to conduct site-directed mutagenesis on the potential phosphorylation sites. AtHAK5cDNA and17AtHAK5mutations on different sites were transformed to athak5mutant and14stable expressed T3generation transgenic plants were obtained through multiple generations of selection. Under50μMKCl,150μM CsCl, athak5mutant showed specific phenotype of root growth inhibition. If AtHAK5cDNA were transformed to athak5mutant, athak5mutant will lose its specific phenotype, and revert to the wild type phenotype. If AtHAK5cDNA with point mutation site, proposed this site plays important roles in AtHAK5, were transformed to athak5mutant, athak5mutant will not revert to the wild type phenotype. We can identify function and no function sites of AtHAK5by phenotype analysis based on the above characters. We found that T549A and T666A were no function sites, F85L, T86A, T311A, T359A, P551S, D552N, S603A, S604A, K668E, S698A and V713L were11function sites. The result will provide a theoretical foundation and scientific basis for understanding the molecular mechanisms of hypokalemia signal transduc-tion in plant cells, and cultivating new varieties of crops which can efficiently absorb and use potash.